(40) The length of time that the Israelites lived in Egypt was four hundred and thirty years;
(41) at the end of the four hundred and thirtieth year, to the very day, all the ranks of the Lord departed from the land of Egypt.
(42) That was for the Lord a night of vigil to bring them out of the land of Egypt; that same night is the Lord‘s, one of vigil for all the children of Israel throughout the ages.
(40) The length of time that the Israelites lived in Egypt was four hundred and thirty years: If we make the calculation according to the chronology given above (6:18), we see that 430 years could not have elapsed from the moment Jacob’s family came to Egypt until the Exodus. Kohath, Levi’s son, was among those who came to Egypt with Jacob (Gen. 46:11), and all the years of his life (133) and of his son Amram (137) and of Amram’s son Moses until the Exodus (80) do not add up to 430 – especially since the years of their lives overlap, rather than being consecutive.
Jewish tradition tells us that the 430 years of Egyptian bondage begin from the “Covenant between the Parts” which God concluded with Abraham, telling him: “Know well that your offspring shall be strangers in a land not theirs, and they shall be enslaved and oppressed four hundred years” (Gen. 15:13). Those four hundred years are calculated from the birth of Isaac, and the actual time that the Jews lived in Egypt was in fact no more than 210 years.
At the same time, and strictly speaking, it would seem that the Jews really should have remained in Egypt the full 430 years. But God reduced the period of Egyptian slavery, because the Jews found their plight so unbearable that they might have perished outright had God not brought the redemption when He did. The Almighty therefore brought the Jews out of Egypt after only 210 years, and He counted the 430 years of slavery of the original decree as having begun from the moment of the Covenant between the Parts (such that the 400 years indicated there begin with the birth of Isaac).
The idea that the Jews spent less time in Egypt than originally planned also explains why God led the Jews to the Land of Israel not directly, but in a roundabout path via Mount Sinai, where the giving of the Torah took place. See §14.1 below for details.
(41) At the end of the four hundred and thirtieth year, to the very day, all the ranks of the Lord departed from the land of Egypt: The Midrash comments on this verse: “The Almighty did not delay the redemption for even a moment. As soon as 430 years had passed from the time that God had concluded the covenant with Abraham, He brought the Jews out of Egypt on the exact day according to that calculation, which fell on the fifteenth day of the month of Nisan.”
(42) That was for the Lord a night of vigil: Leil shimurim, literally, “the night of watchfulness.” It is the night of God’s special vigilance and protection, because on this night the Almighty Himself protected the Jews, not allowing death to enter their homes.
That same night is the Lord’s: It is “the Lord’s night” because He prepared it in advance. That is, from the very beginning God had scheduled the Exodus to take place on this exact day on the calendar. According to the Midrash, and as we have noted, the angels who visited Abraham (Gen. 19:1 ff.) came to him on the fifteenth of Nisan, to give him the news of Isaac’s birth that would happen exactly one year later. Thus, the four hundred years of Egyptian slavery that culminated in the Exodus were calculated not only from the year of Isaac’s birth, but from the day of his birth.
One of vigil for all the children of Israel throughout the ages: Recalling that the Almighty vigilantly guarded the Jews that night, the Jewish nation must in future vigilantly “keep this night,” and celebrate it without fail each and every year.